Still, the Romans were inveterate abbreviators, so I'm guessing it started quite early. So much of Latin is text-speak.
Wondering this just now (when I should have been marking) the obvious fact presented itself to me - having eluded me for half a century - that the Roman numeral C is short for "centum", and M is short for "mille". Okay, I'm sure you all put II and II together long ago - but still it prompts the question, what do I, V, X, L and D stand for? And if for nothing, why those letters and not others?
Answers on a titulus. [ETA Okay, I see Wiki actually has an article all about this, but I'm definitely open to further, ultra-Wiki thoughts.]